When oligomerizing light olefins within a refinery, there is frequently a desire to have the flexibility to make high octane gasoline, high cetane diesel, or combination of both. However, catalysts that make high octane gasoline typically make product that is highly branched and within the gasoline boiling point range. This product is very undesirable for diesel. In addition, catalysts that make high cetane diesel typically make product that is more linear and in the distillate boiling point range. This results in less and poorer quality gasoline due to the more linear nature of the product which has a lower octane value.
The oligomerization of butenes is often associated with a desire to make a high yield of high quality gasoline product. There is typically a limit as to what can be achieved when oligomerizing butenes. When oligomerizing butenes, dimerization is desired to obtain gasoline range material. However, trimerization and higher oligomerization can occur which can produce material heavier than gasoline such as diesel. Efforts to produce diesel by oligomerization have failed to provide high yields except through multiple passes. There is a need of some refiners to have the ability to make more aromatics in an FCC unit. Aromatics in the gasoline stream can be used within the refinery to produce very valuable xylenes. Catalysts utilized for oligomerizing light olefins to produce oligomers typically produce aliphatic gasoline or diesel range compounds which can forwarded to an FCC unit for cracking to propylene. There is a need for making more aromatics in an integrated FCC-oligomerization unit.